Gaseous discharge tube



April 19, 1938. E. F. LOWRY GASEOUS DISCHARGE TUBE Filed Aug. 26. 1956 INVENTOR Evy/'27 Flow/ 4 WITN ESSES:

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ATTORNE Patented Apr. 19, 1938 orr is East Pittsburgh, Pa, a corporation of Penn- Sllvania Application August 26, 1936, Serial No. 97,974

6 Clai ms. (01.250-275) My invention relates to discharge tubes and especially to such tubes having a gaseous atmosphere therein from a vaporizable substance.

An object of the invention is to lengthen thedischarge path between the cathode and .the anode so that material from the cathode will not sputter on the anode and create back emission.

Another object of the invention is to decrease the tendency of such tubes to vary their characteristics with a change in the ambient temperature.

One of the common forms of tubes having a vaporizable substance for creating a gaseous atmosphere is that of the hot cathode mercury vapor type. The gaseous atmosphere is provided by a globule or more of mercury. Changes in temperature of the device result in a change in vapor pressure with the result that the characteristics of the tube are changed. One cause of this variation vapor pressure is that the globule of mercury is generally at a position in the bottom portion of the tube far removed from. the discharge path between the cathode and anode with the result that the temperature around the bottom portion of the tube will affect the vapor pressure. With diiferent ranges of temperature, the control characteristics of the tube, for example, Will vary by several volts.

It is one of the specific objects of my invention to provide means for reflecting heat from the cathode onto this mercury so that the mercury may be speedily vaporized when the tube is put in operation and also that changes in the ambient temperature will have a less percentage effect on the temperature of the mercury vapor.

Other objects of my invention will become evident from the following detailed description taken in conjunction with the accompanying drawing, in which:

The figure is a view in cross section of a tube disclosing a preferred embodiment of my invention.

The tube M has the usual reentrant portion 1 comprising a press l2 surrounded by the annular trough IS. The trough 53 provides a pocket for the vaporizable substance such as the mercury I5. This mercury may, of course, be one or more globules. I have disclosed the trough I3 as having this pocket, but it is apparent that other types of pockets may be utilized for holding the condensed metallic liquid. A cathode I4 of the type adapted to be heated is supported on the press by the lead-in supports Hi. This cathode may be of any suitable type, but I prefer to utilize the edgewise wound helical ribbon type coated with barium and strontium oxide, such as is disclosed in my Patent 1,968,608, issued July 31, 1934. An anode i7 cooperates with this cathode and is preferablylocatedat the upper end of the tube with a leadsupport l8 passing through this upper portion of the tube.

For the various objects of my invention heretofore mentioned, I provide a member 20 preferably having a bulge 2| towards the anode and located in What would be normally the direct discharge path between the cathode and anode. This central portion 2| of the member is imperforated so that material on the coating of the cathode l4 cannot sputter onto the anode and cause back emission. The cathode I4 is located within the inner portion of this bulge 2|, so that the electron path Will necessarily have to be a round about path to the anode While the bulge 2| may be of any suitable configuration, as far as preventing sputtering on the anode and for lengthening the discharge path yet for the purpose of bringing the mercury vapor speedily up to the desired pressure, I prefer to curve the inner portion 22 of this member in a parabolic or spherical shape. The purpose of curving this member is to provide a surface that will reflect the heat from the cathode to the pocket l3 containing the condensed mercury. The lines 23, 24, 25, 26, 21, 28, 29, and 3|] indicate the paths of heat waves from the cathode that are reflected to the surface of the mercury in order to aid in the vaporization of the same.

Materials similar to mercury may, of course, be used. In some devices light sensitive materials may be desired and my invention contemplates providing a reflecting means such as the member 2| for reflecting the light from the hot cathode onto such substances. In other words, my invention is suitable for the reflection of radiant energy Whether this energy be heat or light.

The member 22 may act as a grid or control member by utilizing one of the supporting members 3|, 32 as a lead for the application of any desired potential thereto.

The outer portion of the member 2|! may be perforated, as shown at 33, for the passage of electrons and positive ions therethrough. It Will be noted that the electrons from the hot cathode will have to pass downward to the holes 33 and then back up to the anode IT. This reverse path of the electrons will prevent any sputtered material from the cathode reaching the anode IT. The member 2|] will also act as a very effective radiation shield for the heat energy produced by the cathode and will keep the metallic liquid in the lower portion of the tube suitably vaporized.

Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art.

I claim as my invention:

1. A discharge tube comprising a container, a cathode adapted to be heated, an anode cooperating with said cathode, a vaporizable medium in said container having a position, when not vaporized, away from direct radiation paths from the major portion of said cathode, and means reflecting radiant energy from said cathode to said vaporizable medium.

2. A discharge tube comprising a container, a press, a cathode adapted to be heated supported on said press, a pocket beside said press, a vaporizable medium in said pocket, and means for reflecting radiant energy from said cathode to the vaporizable medium in said pocket.

3. A discharge tube comprising a container, a. re-entrant portion of the container having a pocket therein, a vaporizable medium in said pocket, a cathode supported on said reentrant portion and means reflecting radiant energy from said cathode to the vaporizable medium in said pocket.

4. A discharge tube comprising a container having a cathode and anode, a member extending across the container between said cathode and anode and having a bulge toward said anode, said cathode being within the bulge part of said member and a connection for the application of electrical potential to said member.

5. A discharge tube comprising a container having a cathode and anode, a member extending across the container and having a bulge toward said anode, said cathode being within said bulge, the portion of the bulge directly between said anode and cathode being imperforate.

6. A discharge tube comprising a container having a cathode and anode, a member extending across the container and having a bulge toward said anode, said cathode being within said bulge, the portion of the bulge directly between said anode and cathode being imperforate the outer portions of said member having perforations.

ERWIN F. LOWRY. 

